As LSI chip, including CPU, driver IC, and memory that are used in electronic devices such as a personal computer, a digital video disc, and a cell phone, advances toward a higher performance, a higher speed, further downsizing, and a higher integration, they themselves generate significant heat thereby leading to temperature rise of the chip due to this heat, which in turn causes malfunction and destruction of the chip. Therefore, in order to suppress the temperature rise of the chip in action, many methods for heat diffusion and heat-diffusing members used for it have been proposed.
In the past, in electronic devices and so forth, in order to suppress the temperature rise of the chip in action, a heat sink in which a metal plate having a high thermal conductivity made of such materials as aluminum and copper has been used. This heat sink conducts a heat generated by the chip thereby releasing the heat from its surface by utilizing the temperature difference with the outer environment.
In order to efficiently conduct the heat generated from the chip to the heat sink, it is necessary to intimately contact the heat sink to the chip; however, there are a difference in heights among chips and a tolerance caused by assembling of them. Therefore, a flexible sheet or grease is inserted between the chip and the heat sink, whereby thermal conduction is realized from the chip to the heat sink through the sheet or the grease.
A heat-releasing material in the grease form can be made thin, and thus, this is an excellent heat-releasing material; however, this material is difficult to be controlled. Coating of it is done manually by screen printing or by extrusion from a syringe, or automatically by using a dispenser. However, these methods require a very long time; and besides of it, handling thereof is not easy whereby this process sometimes becomes a bottleneck of a product assembly line.
On the other hand, as to the thermally conductive sheet, mounting thereof can be done merely by adhering it; and thus, a special equipment for it is not necessary, so that handling and control thereof are easier than the grease. However, the adhesion thereof is mostly done manually; and thus, this work is extremely inefficient whereby this process sometimes becomes a bottleneck of a product assembly line. Accordingly, remarkable improvement in productivity may be expected if the mounting process of the thermally conductive sheet can be done automatically by a method using a vacuum nozzle or the like which now became a mainstream method in mounting of a semiconductor part.
As to a feeding method of a thermally conductive sheet to an automatic mounting equipment by using a vacuum nozzle or the like, there is a method in which thermally conductive sheets each of which is previously cut into a prescribed size are set out on a substrate such as a PET film or on a resin tray, whereby the sheets are taken up one by one by means of a vacuum nozzle. However, in this feeding method, the thermally conductive sheets are set out in a plane thereby requiring a very large space; and in addition, the distance to transport the sheet that is suck up by the vacuum nozzle to the mounting site is different in each sheet. Moreover, there was a problem that if number of the thermally conductive sheets that were set out in a plane was large, the distance to the mounting site became so long whereby increasing a risk to drop the sheet from the nozzle.